In many different heavy equipment machines, an operator cab is supported by a frame of the machine with cab mounts. Cab mounts are available in many different forms and configurations and generally try to isolate the cab from the undercarriage of the machine so as to limit the vibrational impact experienced by the operator when the machine moves or performs work. For example, with a loader traveling over rocky terrain, the chassis, undercarriage, and wheels/track of the loader may be jostled and bounced around considerably, but as the cab is not fixedly mounted to the frame, the play afforded by the cab mounts lessens the effect of that motion on the operator.
Such mounts can be as simple as a mechanical spring or an elastomeric shock absorber offering a fixed level of vibration damping. Other types of mounts are fluid or electro-chemical in nature. Magneto-Rheological (MR) and Electro-Rheological (ER) mounts are two examples of such mounts. Taking a MR mount as an example, generally it includes a housing containing MR fluid, a structure that moves through the MR fluid, and a coil for providing a magnetic field across the MR fluid. By directing current to the coils, not only is the magnetic field created through the MR fluid, but the apparent viscosity of the MR fluid is increased as well. As the structure moves through the MR fluid, increasing the apparent viscosity of the MR fluid makes the mount more rigid.
One example of a MR mount is disclosed in U.S. Pat. No. 7,063,191. The '191 patent discloses a hydraulic mount that includes a decoupler sub-assembly, a body filled with MR fluid, a pumping chamber and a diaphragm chamber. The body may be formed from a flexible, molded elastomer, such that vibrational inputs from the engine elastically deform the pumping chamber to cause fluid transfer between the pumping chamber and the diaphragm chamber through the decoupler sub-assembly for viscous damping. While somewhat effective, such a mount provides no feedback
Another example of a MR mount is disclosed in US Patent Application Publication No. 2007/0257408, published Nov. 8, 2007 to Kenneth Alan St. Clair. et al. The '408 publication discloses a strut with a magneto-rheological fluid damper that includes a tubular housing filled with magneto-rheological fluid and a piston head movable within the tubular housing along its longitudinal length.